Thread forming apparatus



Nov. 4, 1958 w. J. DUDA THREAD FORMING APPARATUS Filed Dec. 10, 1954 5 Sheets-Sheet 2 INVENTOR /I/4z/4MJ Qua/1 ATTORN Y Nov. 4, 1958 w. J. DUDA 2,858,720

' THREAD FORMING APPARATUS Filed Dec. 10, 1954 5 Sheets-Sheet 4 United States. Patent.

THREAD FORMING f APPARATUS William J. Duda, Bloomfield, Conn.

Application December 10, 1954, SerialNo. 474,463-

2 Claims. (Cl. 80--6)- This invention relates to the formationofscrew threads; and to the. correction of. screwv threadsupon-the shanks of bolts, screws, and other screw threaded products, and

more particularly to new andusefulimprovements in apparatus for forming and correcting screw threads by means of rotary thread roll dies.

Although the apparatus of the present invention maybe utilized to form threads in work blanks,-the apparatus is particularly suitable for reforming-threads'in various work pieces which have been damaged by nicks, or burrs, as in the case of milled slots, keyways, grooves, and the like, that cut across the threads.- The present apparatus may also be utilized to iron'out threads by rolling the work pieces between the thread roll dies in the case of the instances where work pieces have been plated to restore their dimension,.. the plating often increases the pitch-diameter-outof proportion to the amount of plating, due' to the irregularities. of the metal deposition upon the thread flanks.

The apparatus of the present invention is adapted to compress such irregularities of metal deposition that have formed on the screw threads and roll them into proper dimensional standards.

Still other objects and advantages of my invention will be apparent from the specification.

The features of novely which I believe to be characteristic .of myrinventionare set forth herein and will best be understood, both as to.their fundamental principles and as to their particular embodiments, by refer-' ence to the. specification and accompanying drawings, in which:

Figure l is atop plan view, partly in phantomoutline, of the apparatus-of the present invention;

Fig; 2 is a side elevation partly in ph'antom'outline of the apparatus shown inFig. 1;

Fig. 3 is a somewhat 'enlarged perspective and exploded viewcf a portion of theapparatus of the present invention;

Fig. 4 is a bottom perspective view of the portion of Fig. 3 which is separated from the remainder of. the machine; i

, Fig. 5 is a topwiew, partlyqin section and partly in. phantom 'outline, taken on line '55 of Figs. 2 and 7;

Fig. 6 is a top view, partly in section and partlyin phantom outline, taken on line 6'6 of'Figs. 2 and. 7;

Fig. 7 is an;enlarged.view, partly in section, taken along line 7'.7 of Figs. 1, Sand 6;

Fig. .8 is a .view. partly in. section taken. on line 8-8.

of Fig. 3, some parts being omitted; and

Fig 9. is a view, .partly. in section and partly in: eleva tion, taken along line 9'9'of Figr 7.

Referringmow to. the. drawingsin detail, and particularlyto Figs. 1 and 2, theapparatus of the-present-im vention comprises. a principal casing generally designated- 21,,havings a..horizontal' floor plater22, a. front vertical, wall.'23 ,--.-a rear. verticahwall-M, and side panels 25 and 26. It will be noted that front wall 23is substantially lice,

. 2 twice as high as rear wall 24, while side panels 25*-and 26 are somewhat L-shaped;

Panel 25 has ant-shaped recessformedby a vertical edge27 and a horizontal edge 28- (see Fig. 3), while panel 26' has a. similar L-shaped recess formed by vertical edge 29 and horizontal edge 30.

A cover plate 31 is-mountedton the upper extremit es of wall 23 and the upwardly extendingportions of panels 25 and 26. A partition: 32 is moved horizontally between floor plate 22- and cover plate 31, the sides of said plate extending substantially to the corner of the-L-shaped recesses in panels25rand 26.

The foregoing L-shapedrecesses accommodate a secondary casing, generally:designated-'35:-(see Figs.- l, 2; 3), having a top panel 36g-xrear wall 37], side panels 38- and 42, and a bottom plate 43; V

It will be noted that all of; the walls, panels and partitions of the foregoing principal casing and the secondary casing are firmly'secured at or adjacent their edgesby screws, welding, casting, orthe like. V

Mounted upon the outside. of .panel 25is a pair of guide bar blocks 45-and 46, having guide apertures 47 and 48,- respectively, aligned axiallywitheach'other.- see Figs. 1 and 3. Mounted upon the outside'iof panel 26 is a similar pair of guide bar'blocks 52 andf'53 having guide apertures 54 and 55, respectively, axially aligned with each other.

Wall 38 of secondary casin'g 351is providedawith a pair ofanchor blocks 57'and 58 having apertures 62xand 63, respectively, axially.aligned witheach other. Wall142'is also provided. with a pair of similaranchor blocks 64and 65, having axial apertures 66 and 67 respectively; axially alignedwith each other.

Walls 38 and 42 of secondarycasing ,35.;ar'e spaced apart a distance equal; to-thedistancebetween-walls 25 and. 26 of principal casing 21, whereby said-:secondary casingis adaptedto slide backand forth llpQlllhfighOl'l zontaledges -28 and.30; of walls 25"'-and 26;within.the L.- shapedzrecesses therein. Thev height of walls 38-and 42ris substantially equaltotheheight ofvertical-'edgesf27 and 29 of the L-shaped recess, whereby cover plate 3610f casing 35 .is substantially in thesameplane-with the cover plate 31 of casing. 21.

Substantially parallel guide bars 71 and72=-(Fig.---,1):; are provided to; cause. secondary .casing 35 to move fore ward and backward. within the. L-shaped reeessof principal casing 21. This is accomplished by; guide bar 71. being movably extendedthroughthe aperture; of guide bar blocks 45 and 46 in. casi-ngZl, and extendingthrough; anchor blocks 57 and 58. mounted. on casing. 35. While; guide bar 71 is' freely movable. longitudinallythrough blocks 45 and- 46, it is secured fast within blocks 57 and; 58 by means of .sets screws 73,.or the-like. Similarly, guide bar 72 extends movablythrough,blocks-52 and 53 on casing 21, and is secured fast within anchor-blocks 64 and 65 on casing 35 by set screws 73.

I The forward ends of guide barsfll and 72 are con nected to each other by. means of cross bar ,74 whereby.

the forward and rearward motion of cross bar 74-causes1 corresponding joint rectilinear. motion on the, part of,

guide bars 71 and 72. The forward and rearward mo, tionof guide bars 71 and 72 also cause thecorrespond; ing motion on'the part of casing35 relative to casing 21,

In some embodiments, the set screws 73 in therespective blocks 57, 58, 64 and 65, are adequate frictionally to engage the surface of guide bars 71 and 72, respectively, to cause the movement of casing 35, but since in some cases'there is considerable-force exerted in the forward motion of casing 35 (to the left in Fig; 1), there is provided additionally a thrust ring 75 which is secured -to the end" of each guide bar 71 and 72 by means of screws 76 axially threaded into 3 theends of said. bars. Thus, the forward motion of bars 71 and 72 (to the left in Fig. 1), will cause rings 75 overlying the rear faces of blocks 58 and 65, to move casing 35, thereby relieving set screws 73 from any possible excess friction and preventing them from scoring the surfaces of bars 71 and 72.

The extent to which secondary casing moves to the left in Fig. 1 is determined by the adjustment of screws 76 on guide bars 71 and 72 while set screws 73 are disengaged from said guide bars. .This is also determinative of the requisite pressure that is to be exerted by the thread rolling dies upon the work piece in the apparatus. The adjustment of screws 76 determines the position of thrust rings 75 against which blocks 58 and 65 abut, after which set screws 73 may be turned to engage guide bars 71 and 72, thereby stabilizing the motion of casing 35 relative to casing 21 and of the cooperation of their respective parts.

The lateral motion of cross bar 74 is controlled by means of a roller cam and lever arrangement mounted on said cross bar- See Figs. 1 and 2. This mechanism comprises a pivot pin 82 extending vertically through cross bar 74 and upon the ends of which is pivotally mounted a pair of substantially parallel horizontal lever plates 83. Mounted between the rearward portion of lever plates 83 is a roller locking cam 84 which rotates freely, around pin 85 secured Vertically between plates 83,;said cam being adapted to roll against wall 23. Connecting the forward ends of plates 83 is a vertical cross piece 86 to which is attached a suitable arm 87 whose handle 88 may be grasped by the operator to move plates 83 around their pivot pin 82.

In order to limit the motion of plates 83, and accordingly roller 84, there is provided a stop pin 91 threadably inserted into cross bar 74, and against the top of which cross piece 86 abuts when cam 84 reaches the desired locking position. This locking position may be varied as desired by adjusting screw 91 and fixing it in position by means of lock nut 92.

In order to limit the rearward motion of secondary casing 35 (to the right in Fig. 1), ring 96 is provided on each guide bar 71 and 72 intermediate blocks and 46 and between- 52 and 53, respectively. Rings 96 are adjustably secured at suitable positions on guide bars 71 and 72 by means of set screws 97. Since rearward movement of rings 96 is limited by blocks 46 and 53, respectively, the rearward motion of casing 35 will accordingly be limited by the same distance. It is unders'tood that the extent of movement of casing 35 may be predetermined in accordance with the requirements of the operation of the apparatus. 7

When roller cam 84 is moved to an unlocking position by moving arm 87 to the left, the release of pressure permits guide bars 71 and 72 to move rearwardly (to the right in Fig. 1) by the action of springs 98 mounted around bars 71 and 72, and positioned between blocks 45 and 52 and the respective rings 96 mounted on said guide bars.

Partition 32 in casing 21 has a convex extension 102 at its rearward edge, on the top surface of which is mounted a hold down ring 103 by means of suitable screws or studs 104. See also Fig. 9. Positioned axially relative to said ring and extending upwardly is a cylindrical anvil 105 having outwardly extending flange 106 at its lower end which is engaged by ring 103 and is adapted to move freely within restricted limits in recess 107 of said ring.

Extending Vertically through the axial aperture of anvil 105 is an ejector plunger shaft 111 which is movable longitudinally through suitable apertures in partition 32 and bottom plate 22. Mounted on the top of plunger shaft 111 is a plunger head 112. Threadably secured to the lower end of plunger shaft 111 is a stop ring 113, the upper surface of which abuts. stop Plate 114, which is attached by suitable means (not shown) to the bottom plate 22, said plunger shaft 111 being movable freely through stop plate 114. A bracket 115 is mounted by suitable means (not shown) to the bottom of the plate 22 and is provided in order to serve as a support for spring 116, mounted between bracket 115 and stop ring 113. Spring 116 normally urges shaft 111 upwards to the limit of its motion as determined by the position of stop ring 113 on shaft 111. It is evident that the ultimate stop position of cap 112 may be predetermined by adjusting stop ring 113 on the lower end of shaft 111.

There is also provided stop screw 117 threadably inserted axially into the lower end of shaft 111. Screw 117 limits the downward motion of plunger shaft 111 when the head of screw 117 abuts the bracket 115. It is evident that the lower limit of motion of shaft 111 may be predetermined as desired by adjusting 117 in the end of plunger shaft 111 The function of anvil 105 and plunger shaft 111 will .be more fully explained and described hereinbelow.

It will be noted that the bottom plate 43 of secondary casing 35 has a concave recess 121 shaped to accommodate the convex extension 102 on partition 32 of the principal casing 21, when the secondary casing is brought into close proximity to the principal casing in its forward motion.

In order to accommodate the work piece upon anvil 105, there are provided in cover plates 31 and 36 substantially semicircular beveled recesses 123 and 124, respectively, positioned opposite each other and through which the work piece may be inserted and withdrawn relative to theapparatus. 1

When the machine is in its assembled position, as shown in Figs. 1, 2 and 7, it will be observed that partition 32 and bottom plate 43 serve to divide the'apparatus into a lower chamber 127 and an upper chamber 128. Lower i chamber 127 contains the operative gear train-mechanism, while upper chamber 128 encloses the thread roll dies and the work piece. It will be noted from said figures that box-like casing 21 forms jointly with box-like casing 35 a substantially unitary protective enclosure for both the gear train mechanism and the thread forming dies, whose operations will be more fully described hereinbelow.

Operating power for the apparatus of the present invention is derived from an electric motor or the like, not shown, the output of which is attached to the lower end of input shaft 131 (Fig. 7), which is mounted vertically and rotates within suitable bearings in cover plate 31;

partition 32, and bottom plate 22. Mounted fast on drive shaft 131 and rotated thereby are a first drive gear 132 and a second drive gear 133. Gear 133 meshes with and rotates an idler gear 134 mounted on shaft 135, positioned vertically in suitable bearings within cover plate 31, partition 32, and bottom plate 22. Gear 134 engages gear 136 (Fig. 6) mounted fast upon vertical shaft 137, the latter rotating within suitable bearings in cover plate 31, partition 32 and bottom plate 22.

Mounted fast in bottom plate 22 to the right of gear 132 is a vertical stub shaft 141 around which idler gear 142 rotates freely and which meshes with and is rotated by drive gear 132.

When secondary casing 35 is moved to the left (Figs. 1 and 6) into the operative position, a driven gear 144 is moved into meshing relationship with idler gear 142. Driven gear 144 is mounted fast to a vertical shaft 145 rotating in suitable bearings in cover plate 36 and bottom plate 143 of secondary casing 35. Also mounted fast on shaft 145 is a second gear 146 which is caused to rotate with the rotation of shaft 145.

Supported vertically in cover plate 36 and bottom plate 43 is a shaft 147 whose lower end extends below plate 43 and at the lower end of which is mounted idler gear 148 adapted to mesh with and be driven by gear 146. Idler gear 148 is adapted to engage and rotate gear 152 keyed pair of shafts mounted in a's'eparable casing which is brought into operative connection with a principal casing, the foregoing gear train accomplishes this result and also :provides for rotation in the same direction vofthe principal operative working shafts, 131, 137, 145 and 153.

It will be noted that when secondary casing 35 is re-v leased and moves rearward, and while the gears are still rotating under the action from continuously rotating shaft 131, although gear 144 will move to the right (Fig; 6), it will still remain meshed with gear 142 since ,the movement of casing 35 is of the order of to of an inch, or more in special thread applications, and is not sufiicient in ordinary practice to draw gear 144 out of engagement with gear 142. Thus, shafts 145, 147 and 153 will continue rotating, and keep the machine in readiness for quick repeated operations when casing 35 is brought back as inFig. 1. Thus, it is unnecessary for the operator to turn off the power while replacing the work pieces in the machine. Rings 96 are adjustably secured to guide bars 71 and 72, respectively, at equal distances from blocks 46 and 53, respectively, said distance being determined by the limit of. displacement between gears 142 and 144, within which they will continue to remain operatively meshed with each other.

On those portions 'of shafts 131, 137, 145 and 153, that extend through the upper chamber 128, there are mounted a thread roll die 161, 162, 1 63, and 164, respectively, each of said dies beingkeyed to said shafts by means of 'set screws 165,or the like. Thread roll dies 161, 162, 163 and 164 rotate on their respective shafts at an equal speed as predetermined by the appropriate selection of the dimensions of the gear train in chamber 127. Each of the thread roll dies 161, 162, 163 and 164 are bounded on top and bottom by thrust Washers 167 which serve to stabilize the position of said dies and the rotation of their respective shafts.

Each of the dies 161, 162, 163 and 164 have peripheral threaded working faces 168, which are suitably hardened and which are adapted to form a negative impression of their contours into the workpiece.

In operation, lever handle 88 is grasped by the operator and moved to the left (see Fig. 1), whereby lever 86 is L rotated on its pivot 82 causing roller cam 84 to move downward, thereby releasing pressure between wall 23 of upper casing 21 and cross bar 74. Upon release of this pressure, springs 98 urge rings 96 to the right-andrnove guide bars 71 and 72 to the right, to a distance limited by the abutment of rings 96 against the end wall of blocks 46 and 53, respectively. With the motion of guide bars 71 and 72, secondary casing 35 also moves to the right and widens the space between recesses 123 and 124.

A cylindrical work piece, upon which'it is desired to form threads on its peripheral surface, or whose preformed threads are to be deburred or corrected, is moved into position over anvil 105, its lower end resting upon hold down ring 103. Thereupon, the operator moves lever arm 87 back to the right (Fig. 1) causing cam roller 84 to press against wall 23 and guide bars 71 and 72 move to the left carrying secondary casing 35 to the left. Thread roll dies 163 and 164, which are mounted in secondary casing 35 approach the work piece, and when said casing is locked in position, the work piece is caused to be engaged jointly by all of the continuously rotating thread roll dies 161, 162, 163 and 164, whereby the work piece is rotated between them. The rotating thread roll dies produce a negative impression of die faces 168 upon the peripheral surface of work piece and reforms or deburs the threads thereon. In the case where worn threads on the work piece have been built up by electroplating or the like, and the plating is not altogether evenly distributed over the threads, the thread roll dies of the present apparatus will iron out these irregularities new J lower areas.

It is to be noted that the actual thread rolling or thread correcting takes place upon the work piece in the period of time required for said dies to rotate a minimum of onequarter ota turn, where the diameter of the work piece is substantially equal to the diameter of the dies. Where burnishiiig of the threads on the work piece is required, it may be desirable to operate the machine for a longer interval of time during which the thread roll dies rotate for a considerable number of turns. The speed of the threadroll dies may be increased or decreased depending upon the diameter of the work piece that is being processedand other operating conditions. 7

In other embodiments the diameter of the thread roll dies may be multiples of a particular work piece diameter, in which case appropriate gears may be selected for driving said dies at the requisite speed for the thread cutting of thread rolling operation.

' When in operating condition, the axes of the respective thread roll dies are spaced apart symmetrically as in the'four corners of a square. The purpose of this 'symmetrical array is to insure the symmetrical engagement of the work piece by'the thread roll dies. Were the apparatus of the present invention to comprise only three thread roll dies, and the work piece has longitudinal key- Ways or slots, it is apparent that when one of said dies is traversed by such akeyway or slot as the work piece rotates, either the work piece would be asymmetrically displaced, or thefparticular dies under lateral pressure would be asymmetrically displaced, thereby preventing the even and symmetrical thread formation or thread correction.

After the work piece has rotated a suflicient number of turns for threadroliingor thread correcting, the operator moves lever arm 87 to the left' thereby moving the secondary casing 35 and thread roll dies 163 and 164 to the right, thereby releasing the work piece from the dies, at which time the operator can manually remove the work piece from the apparatus and insert another work piece. I

It will be noted that screw 91 is adjustable and is set in position to act as a stop for roller cam 84 when lever 87 is movedsufliciently to the right (Fig. 1) to cause roller 84 to pass slightly beyond the center line of pressure upon wall 23, thereby causing cam 84 and lever plates 83 to remain locked in position during the cycle of operation. Thus, the operator of the apparatus need not maintain continued pressure on the lever arm 87 during the thread rolling or thread correcting process.

In the event that an oversize work piece is inserted by chance into the apparatus, the operator can, by ex perience, instantly sense the resistance of the apparatus in closing upon the Work piecesince the lever arm 87 will not move to the maximum stop position determined by the setting of screw 91, and thus before any excessive pressure is imposed, the operator can again move lever arm 87 to the leftit'o remove the oversize work piece.

The provision of a floating anvil serves to support the cylindrical work piece that is rolled between the dies, and its outside diameter is selectedto be sufliciently close in dimensions to the inside diameter of the work piece so that the latter is prevented from collapsing under the pressure of the dies as 'well as to insure the dimensional standards of the impressions to be made upon the work piece.

The provision for the slight lateral movement of anvil 105 relative to ring 103 and shaft 111 serves to permit the work piece, after it has been processed, to move out of engagement from thread roll dies 161 and 162 when thread roll dies 163 and 164 are moved to the right. Since all of the thread roll dies are-in continuous rotation when the casing is opened and when the operator removes and replaces work pieces, it is important to provide for this safety factor by the work piece becoming easily disenaueing: the high areas and equalizing theiiif with a.

gaged from dies 161 and 162. When work pieces of dif- 'ferent -sizes are to be processed, anvils 105 of different sizes may be provided for their support.

In some embodiments, automatic ejection of the work pieces may be provided by the utilization of the plunger shaft mechanism," In the case where a cylindrical work piece has a capped enclosure at one end, the procedure of inserting the work piece over anvil 105 causes plunger head 112 and plunger shaft 111 to move downward against the action of spring 11610 the position where the work piece is engaged by the thread roll dies and is rotated thereby. As soon as the work piece is processed, and dies 163 and 164 move to the right, plunger shaft 111 and plunger head 112 automatically'move upward under the action of spring 116, and cause the work piece to emerge from the machine above cover plates 31'and 36 to facilitate the grasping and removal of the work piece by the operator; The degree to which the work piece is lowered into the apparatus for thread cutting or thread rolling may be determined by the adjusted position of screw 117 in the lower end of shaft 111. 1

In some other embodiments, where an' open ended cylindrical work piece is to be'processed, and itis desired to provide automatic ejection, the flanged anvil 105 may be arranged to be mounted fast upon shaft 111 and movable longitudinally therewith, so that upon completion of the thread rolling process, the release of the work piece will permit shaft 111' to move anvil 105 upwards, carrying the work piece 'with it. p

Although'the machine of the present invention has been shown positioned horizontally throughout the figures of the drawings, it is'to be understood that it may also be mounted vertically whereby the work piece is inserted and withdrawn in a horizontal motion.' Also, the parts of the machine may be reversed whereby the lever arm may be grasped by the operator's right hand, while the work pieces are handled by the operators left hand.

The machine of the present invention is adaptable for automatic work piece feeding and ejection while the operation of the locking cam may also be performed automatically by suitable mechanisms adapted to the apparatus.

In the specification, I have explained the principles of my invention, and the best mode in which I have contemplated applying those principles, so as to distinguish my invention from other inventions; and I'have particularly pointed out and distinctly claimed the part, mode or combination which I claim as my invention or discovery.

While I have shown and described certain preferred embodimentsof my invention, it will be understood that modifications and changes may be made 'without departing from the function andscope thereof, as will be clear to those skilled in the art.

Iclaim: j

1. A thread forming apparatus comprising a first boxlike casing, a first pair of spaced apart thread forming dies rotatably mounted within said first casing, a first gear train mounted within said first casing. and operative to rotate said first pair of dies, said first gear train being adapted to be operated continually by a suitable motive 'box like' casing movable between either of two locations within said recess in said first casing, asecond pair of spacej'cl a'part thread forming dies mounted within said second casing, a 'second'gear train mounted withinvsaid second'casing andoperative to rotate said second pair of dies, said two pairs of thread forming dies being operative collectively to form a thread upon a work piece positioned between them when said second casing is in one of said locations, said two pairs of dies being retracted from said work piece when said second casing is in the other of said locations, one gear of said first gear train and one gear of said second gear train being continually meshed with each other when said second casing is in either of said locations, said first casing and said second casing jointly forming a substantially unitary enclosure for both of said pairs of thread forming dies and for both of said gear trains, a pair of guide bars connected to said second casing, a pair of guide blocks connected to said first casing, each of said guide bars being movable longitudinally relative to a respective guide block, a ring adjustably connected to each of said guide bars, said rings being adapted to abut said guideblocks and limit the displacement of said second casing from said first casing, a spring connected between each of said rings and said first casing, said springs normally urging said second casing-apart from said first casing, the position of said rings being determined by the limit of displacement within which the meshing gears of said first and second gear trains continue in operative engagement, a cross bar connected between said guide bars, and a lever connected to said cross bar, said lever being adapted to impinge upon said first casing to cause the movement of said second casing toward said first casing.

2. A thread forming apparatus according to claim 1, and further comprising a circular anvil on said first casing andaround which a work piece is adapted. to be mounted, an annulas on said anvil and a circular ring connected to said first casing and surrounding said annulus, the internal diameter of said ring being slightly larger than the external diameter of said annulus whereby the latter is capable of limited lateral movement within said ring to permit the automatic centering of said work piece when said dies are moved to their operative positions.

References Cited in the file of this patent UNITED STATES PATENTS Denmark Feb. 11, 1918 

